The reaction between magnesium and hydrochloric acid
Aims
Magnesium and dilute hydrochloric acid react together according to the equation below:
magnesium + hydrochloric acid → magnesium chloride + hydrogen
The hydrogen produced makes the reaction mixture effervesce (fizz).
The faster the reaction, the shorter the time taken for the effervescence to stop.
You will study the effect of changing the concentration of hydrochloric acid on the rate of reaction.
Apparatus
Goggles
Bench mat
Teat pipette
Stop clock
100cm3 beaker
25cm3 measuring cylinder
5 x 1cm pieces of magnesium
2.0M hydrochloric acid
Method
Eye protection
must be worn
1.
Measure 25cm3 of 2.0M hydrochloric acid and put it into the beaker.
2.
Put one piece of magnesium into the beaker of hydrochloric acid, and time the reaction.
Record the reaction time in a table like Table 1 (below).
Concentration
of acid (M)
2.0
1.6
1.2
0.8
0.4
3.
Reaction
time (s)
1
time
(s–1)
Table 1
Empty the beaker and rinse it out.
Repeat the experiment using the other volumes of hydrochloric acid and water shown in Table 2.
Volume of hydrochloric
acid (cm3)
20
15
10
5
Volume of
water (cm3)
5
10
15
20
Concentration
of acid (M)
1.6
1.2
0.8
0.4
Table 2
Analysis of results
1.
Work out 1 ÷ time for each reading, and write the answer in the third column of your Results table.
2.
Plot a graph of 1/time (vertical axis) against the concentration of hydrochloric acid (horizontal axis).
Note: it sometimes helps to multiply each number by 1000 to get easier numbers to plot on your graph.
3.
Explain what your results tell you about the reaction between magnesium and hydrochloric acid.
N-m07-18 (© Nigel Saunders 2000)